A MONOGRAPH OF THE SEA-SNAKES (HYDROPHIINJE). 181 



in sea snakes in common with many other creatures. This laxity is to be seen 

 especially in the bloated features, puffy lips, and about the chin shields of senile 

 specimens which alters the approximation of the shields, obliterates their detail, 

 destroys the clearness and definition of the head lines to such a purpose, that 

 a dapper juvenile specimen of the same species appears a different creature. Figures 

 22 and 25 exemplify this statement. Incase, however, my views with regard to these 

 two forms being identical are not shared by others, I may say that I have seen as 

 great a difference in general aspect between young and old specimens in such well 

 differentiated species as Enhydrina valakadyn. 



With the exception of the characters above made reference to I can find none 

 which possess any weight at all in the separation of the species, and, as has been 

 already remarked, many of those referred to are subject to some degree of inconstancy 

 in certain species, making them at the best of somewhat uncertain value. Many of 

 these very characters, however, cannot be dispensed with ; they are essential to the 

 separation of the species of Distira, but in making use of them one has to guard 

 against allowing a single or dual aberration to form the basis of a new species as has 

 undoubtedly so often been the case. Naturally it is the species that most lack definite 

 characters that have suffered most separation and confusion, especially Distira spiralis 

 and cyanocincta. 



It is more than probable that many of my views expressed above may not be 

 completely shared by other herpetologists, and I would remark that I believe that 

 the only possible way to establish the constancy of the various shields in a given 

 species is by a comparison of these in the gravid female with those of her unborn 

 progeny. My opportunities for doing so have been limited, but in one species in 

 particular I have been fortunate viz., Enhydrina valakadyn. I have had many gravid 

 females, and examined the scale characters of each attentively with that of their 

 contained foetus. The result was instructive, and modified my previous views consider- 

 ably. The inconstancy of many shields relied upon by other authors implicitly in 

 classification was found to be proximately similar in the few gravid females of other 

 species, notably those of the genus Distira, which fortune has from time to time 

 offered me for examination. 



A series of gravid Distira spiralis and D. cyanocincta would alone, I feel assured, 

 clear up the conception of these species as viewed by me in partial opposition to 

 those held by other herpetologists. So far as the numbers of the costals and ventrals 

 are concerned, I think it is reasonable to expect to find a proximate range of varia- 

 tion in individuals of species which are similar in corporeal habit. Now if one takes 

 a well differentiated species such as Enhydrina valakadyn, which could not be confused 

 with any other, the costals in the neck according to Mr. Boulenger's showing- 

 vary within twenty in individuals. A similar range is recorded by him for the body 

 scales. The ventrals by the same authority's showing vary by 84. Now in some of 

 the genus Distira, where a large series of specimens is available and these from the 

 widest geographical area, a proximate degree of variation is seen in the costals, and 

 even an excess in the range of the ventrals amounting to 155 in fasciata. Moderate 



